Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

580
FXUS63 KLOT 282246
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
446 PM CST Wed Jan 28 2026

.KEY MESSAGES...

- Cold conditions will continue into the weekend with mainly
  subzero wind chills through Saturday morning.

- Threat for impactful lake effect snow continues to increase
  for Friday into/through Saturday. After likely accumulations
  and impacts in northeast/eastern IL on Friday, the focus may
  shift into primarily northwest Indiana Friday night-Saturday,
  though it could be close for parts of IL.

- There may be a period of light snow accumulations Sunday night
  into Monday, followed by less cold conditions by midweek.

&&

.DISCUSSION...
Issued at 236 PM CST Wed Jan 28 2026

Tonight through Thursday:

It`s a quiet, albeit chilly, Wednesday out there today.
Temperatures early this afternoon sit in the teens but, with a
10-20 mph westerly breeze, wind chills around the area are in
the single digits on either side of zero. A shortwave upper
impulse is diving into the region from the northwest bringing a
corridor of light snow and virga snow across central and
southern IA and into western IL. Precip coverage, if it even
lasts with so much dry air nearby, should stay out of reach to
our south for the remainder of the day. Expect mostly sunny
skies for the rest of today to give way to mostly clear skies
tonight, allowing for another cold night ahead.

Increasing BL moisture over the southern end of the lake could
result in a period of light lake-effect snow showers and
flurries in parts of northwest Indiana late this evening into
early Thursday. Coverage should favor areas east of our CWA and
into southwest lower MI, but light snow will be possible as far
west as the Porter/Lake county line. In the forecast, maintained
some low PoPs mainly around northern and eastern Porter County
where a dusting of accumulation is plausible. Any lingering snow
or flurries will taper off to the east during the morning.

Lows overnight into early Thursday are forecast around to just
below zero. Wind chills at the start of tomorrow are expected in
the -10 to -15 range and staying below zero through the morning
hours. High pressure building into the region during the day
should allow for more mostly to partly sunny skies tomorrow,
albeit with well below normal highs in low-mid teens (offset by
much lighter winds than today/Wednesday).

Doom


Thursday Night through Saturday Night:

For the upcoming potentially impactful lake effect snow episode
Friday-Saturday, while there are still several key items of
lingering uncertainty, we`re starting to gain a bit more clarity
on bigger picture trends.

Here`s a general timeline:

- Friday (6am-6pm CST): A snow band (potentially with embedded
  heavy rates) will likely come ashore sometime between 6 AM and
  noon into northeast Illinois. In addition to producing a burst
  of heavy lake effect snow near the lake, there may be a 1-2 hour
  period of accumulating snow farther inland (unclear exactly how
  far west and south) into northern IL and perhaps parts of
  central IL, with some snow into far northwest Indiana as well.
  The uncertainty regarding time of arrival of the, and exact
  locations and residence time of heavier snow rates lowers
  confidence in the specific details. With that said, the daytime
  hours of Friday are presently the highest confidence timeframe
  (50-60%) for accumulating snow and travel impacts into northeast
  IL/Chicago metro.

- Friday Night (6pm-6am CST Sat): An intense lake effect snow band
  will probably take shape and potentially focus into parts of
  northwest Indiana (particularly Lake IN and Porter Counties/60%
  chance and 40-50% chance into northern Newton-Jasper). Some
  guidance (mainly recent GFS/GEFS simulations) suggests parts of
  northeast and eastern IL could be affected as well (~40-50%
  chance in official forecast) near/east of I-57. Confidence is
  low-medium in the details for this period, though we have medium
  to high confidence that there will be an intense band somewhere
  south of Lake Michigan. This is the most concerning time window
  for a more prolonged period of heavy/intense snowfall rates.

- Saturday (6am-6pm CST): If the heavy/intense lake effect band
  materializes and indeed focuses into northwest Indiana, it may
  meander back west towards the IL shore or even into far
  eastern/northeastern IL. However, this is a significant
  "wildcard" aspect of the forecast. An overall majority of the
  more recent model and ensemble data depicts the lake effect
  focus being primarily northwest Indiana. Once again, the
  GFS/GEFS has consistently depicted the banding shifting or
  remaining farther west into IL. We certainly can`t discount this
  scenario, though in our messaging we plan to emphasize a higher
  likelihood for far northwest Indiana (~60% into northern Lake
  IN). Our forecast confidence is low-medium in the details.
  There`s also uncertainty in how long into the day the core of
  the lake effect snow maintains heavy snowfall rates.

- Saturday Night (6pm-6am CST Sunday): The intensity of the snow
  should decrease during this time. Only about 20-30% of the the
  global ensemble members hang onto organized lake effect snow for
  a part of the night, supporting 20-30% PoPs from the northeast
  IL shore to far northwest Indiana.

Due to the notable uncertainty still evident in the Friday-
Saturday accumulating lake effect snow details, we deferred any
winter weather headlines issuance to a later forecast issuance.

Meteorological Synopsis:

Late Thursday night, very cold air over the still relatively mild
open waters of southern Lake Michigan (not expecting much
deleterious effect from ice cover in the nearshore) will likely
result in the development of a lake induced meso- low accompanied
by heavy snowfall rates. This will be the result of very favorable
thermodynamics augmented by large scale ascent from an incoming
mid-level trough axis. There`s overall solid agreement in this
general scenario.

Into the day on Friday, as is very common in these setups, there`s
a large guidance spread in the evolution of the band out over the
lake. From a somewhat bigger picture perspective, the sharp east
to west mid-level trough axis traversing the region should result
in the meso-low related banding moving southwest into IL. This
could very well have at least 1-2 hours of heavy snow rates near
the lake in IL (including Chicago) given inversion heights almost
up to 10kft and strong ascent through the DGZ. With a time of
arrival variance from as early as 6-7am to as late as 11am-1pm,
this certainly lowers confidence in the details as alluded to in
the general timeline. The band could take on a squall-like
orientation westward into northern IL, though duration of
accumulating snow inland would probably be only an hour or two.

After the passage of the mid-level trough axis late Friday into
Friday night, inversion heights should come down some and
thermodynamics may become slightly less favorable with time. Lake
effect parameters should still remain quite favorable though for a
well organized band and possible mesolow. The consensus low-level
and boundary layer flow orientation (N to NNW) during this time
conceptually favors northwest Indiana, though it`s always tricky
when meso-lows are present. It`s close to impossible at this range
to accurately predict how much or little the heaviest banding may
stall over a given location. With last weekend`s event in mind and
it`s 25-30:1 or higher snow ratios, snowfall rates could
conceivably get out of hand Friday night into Saturday morning in
the heart of the band.

Similar to warm-season convective forecasting, lake effect snow
(also convection) is often affected by what happened prior. So
exact locations are only a rough idea, but again, conceptually
should favor far northwest Indiana. The GFS/GEFS has been most
aggressively far west with the band positioning and also slower to
degrade lake effect parameters. Wobbles in the orientation of lake
induced convergence axis could bring the band(s) back near or
onto the IL shore for a time on Saturday before the snow rates
start to notably diminish. We`re a bit skeptical of the GFS/GEFS
insistence on keeping the band(s) organized all the way into
Saturday evening, so our official PoPs are only in the 30-40%
range Saturday afternoon and 20-30% range Saturday night.

Castro


Sunday through Wednesday:

On the heels of this weekend`s lake-effect event, guidance is
resolving a weakening synoptic wave pushing into the region from
the northwest on Sunday. Quite a lot of uncertainty exists in
the timing and structure of this system, but it looks like a
decent shot at a period of light snow sometime in the Sunday PM
through Monday timeframe. The more aggressive medium range camps
paint a few to several tenths of accumulation around the area,
but we`ll have to see how expectations evolve behind this
weekend`s very dynamic synoptic setup off the east coast. This
ongoing cold stretch, the coldest yet this season, is expected
to gradually give way to more temperate conditions by early next
week. However, near to below normal temperatures are favored
through at least midweek with highs forecast to get up into the
20s and lower 30s.

Doom

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 445 PM CST Wed Jan 28 2026

VFR conditions with northwest winds generally less than 10kt
expected through the TAF cycle.

- Izzi

&&

.HYDROLOGY...
Issued at 230 PM CST Wed Jan 28 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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